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| <td width="21"> <h1></h1></td> |
| <td width="885"> <font face="Verdana, Arial, Helvetica, sans-serif"><b><font size="6">Quick |
| Start </font></b></font></td> |
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| <p>Preprocessing with <tt>Wave</tt> is highly configurable. You must |
| define a few options to control it. Here are a few of the |
| options you can define:</p> |
| <BLOCKQUOTE dir="ltr" style="MARGIN-RIGHT: 0px"> |
| <P><STRONG><IMG id="IMG1" height="13" src="theme/bullet.gif" width="13"></STRONG> include |
| search paths defining where to search for files to be included with |
| <tt>#include <...></tt> and <tt>#include "..."</tt> directives<br> |
| <STRONG><img src="theme/bullet.gif" width="13" height="13"> </STRONG>which |
| macros to predefine and which of the predefined macros to undefine<br> |
| <STRONG><img src="theme/bullet.gif" width="13" height="13"> </STRONG>whether to enable any of several extensions to the C++ |
| Standard (such as for variadics and placemarkers) |
| </P> |
| </BLOCKQUOTE> |
| <p>You can access all these processing parameters through the <tt>boost::wave::context</tt> |
| object. So you must instantiate one object instance of this type to use the <tt>Wave</tt> |
| library. (For more information about the context template class, please refer |
| to the class reference <a href="class_reference_context.html">here</a>.) To instantiate |
| the <tt>boost::wave::context</tt> object you have to supply at least two template parameters: |
| the iterator type of the underlying input stream to use and the type of the lexer iterator to be used as the token source for the preprocessing engine.</p> |
| <P dir="ltr">Do not instantiate the main preprocessing iterators yourself. |
| Get them from the <tt>boost::wave::context</tt> object instead. |
| The following code snippet is taken from the <tt>quick_start</tt> sample, which shows a minimal usage scenario for <tt>Wave</tt>. </P> |
| <pre><span class="comment"> // The following preprocesses a given input file. |
| // Open the file and read it into a string variable</span> |
| <span class="keyword">std::ifstream</span> instream(<span class="string">"input.cpp"</span>); |
| <span class="keyword">std::string </span>input<span class="keyword">( |
| std::istreambuf_iterator<char></span>(instream.rdbuf()), |
| <span class="keyword">std::istreambuf_iterator<char></span>()); |
| |
| <span class="comment">// The template boost::wave::cpplexer::lex_token<> is the |
| // token type to be used by the Wave library. |
| // This token type is one of the central types throughout |
| // the library, because it is a template parameter to some |
| // of the public classes and templates and it is returned |
| // from the iterators. |
| // The template boost::wave::cpplexer::lex_iterator<> is |
| // the lexer iterator to use as the token source for the |
| // preprocessing engine. In this case this is parametrized |
| // with the token type.</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost::wave::cpplexer::lex_iterator</span><span class="special"><</span> |
| <span class="identifier">boost::wave::cpplexer::lex_token</span><span class="special"><> ></span> |
| <span class="identifier">lex_iterator_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost::wave::context</span><span class="special"><</span> |
| std::string::iterator<span class="special">,</span> lex_iterator_type<span class="special">></span> |
| <span class="identifier">context_type</span><span class="special">;</span> |
| |
| context_type ctx(input.begin(), input.end(), <span class="string">"input.cpp"</span>); |
| <span class="comment"> |
| // At this point you may want to set the parameters of the |
| // preprocessing as include paths and/or predefined macros. |
| </span> ctx.add_include_path(<span class="literal">"..."</span>); |
| ctx.add_macro_definition(...); |
| <span class="comment"> |
| // Get the preprocessor iterators and use them to generate |
| // the token sequence. |
| </span> context_type::iterator_type first = ctx.begin(); |
| context_type::iterator_type last = ctx.end(); |
| |
| <span class="comment"> // The input stream is preprocessed for you during iteration<br> // over [first, last)<br></span> <span class="keyword">while</span> (first != last) { |
| <span class="keyword">std::cout</span> << (*first).get_value(); |
| ++first; |
| } |
| |
| </pre> |
| <P dir="ltr">The constructor of the <tt>boost::wave::context</tt> object can |
| take a pair of arbitrary iterator types (at least <tt>input_iterator</tt> type |
| iterators) to the input stream, which must supply the data to be processed. |
| The third parameter supplies a filename, which is reported in the preprocessor output to |
| indicate the current context. |
| Note though, that this filename is used |
| only as long as no <tt>#include</tt> or <tt>#line</tt> directives are encountered, |
| which in turn will alter the current reported filename.</P> |
| <P dir="ltr">The iteration over the preprocessed tokens is relatively straightforward. Just get the starting and the ending iterators from the context object |
| (maybe after initializing some include search paths) and you are done! Dereferencing |
| the iterator will return the preprocessed tokens generated on |
| the fly from the input stream. (To get further information about the token type, |
| you may want to look <a href="class_reference_tokentype.html">here</a>.)</P> |
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| <p class="copyright">Copyright © 2003-2010 Hartmut Kaiser<br> |
| <br> |
| <font size="2">Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) </font> </p> |
| <span class="updated"></span> |
| <p class="copyright"><span class="updated">Last updated: |
| <!-- #BeginDate format:fcAm1m -->Tuesday, July 29, 2008 20:34<!-- #EndDate --> |
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